New Forming Process of Three-Dimensionally Shaped Magnesium Parts Utilizing High-Strain-Rate Superplasticity

Abstract

The applicability of high-strain-rate superplasticity for forming magnesium parts, especially structural component with a boss on a plate designed with the aim of producing mobile electric appliances, was examined. The required microstructure and grain refinement process for target forming was examined prior to the forming trials. Following the examination of the processing design, the high-strain-rate superplastic AZ91 magnesium alloy with a required grain size less than 3.2 mm was produced by hot extrusion under the condition that the Zener-Hollomon parameter was 3 Â 10 12 s À1 . It was experimentally confirmed that a boss with a height greater than 5 mm, which is a requirement for electric appliances, could be formed within 10 s even at a low temperature of 523 K using this high-strain-rate superplastic magnesium alloy. Basic knowledge related to the formation of three-dimensionally shaped magnesium parts by utilizing high-strain-rate superplasticity was obtained.

Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

“…When the initial grain size is large, the m value is estimated to be about 3, which is in good agreement with the value reported in some previous works. 19,24,27,31) However, the m value increases with decreasing initial grain size to be about 8. In the high Z region, there is no initial grain size dependence on d av , and the m value is also about 8.…”

“…[15][16][17][18][19][20][21][22][23][24][25][26][27][28] It has been reported that dynamically recrystallized grain size (DRX grain size) decreases with an increase of Zener-Hollomon parameter (Z-parameter) 29) in several magnesium alloys. 19,24,27,30,31) Watanabe et al have reported that there is initial grain sizes dependence on DRX grain size in AZ61 magnesium alloy. 19) However, there have little reports on such initial grain sizes dependence on DRX grain size in other magnesium alloys.…”

Effect of Tool Materials on Dynamic Friction Characteristics and Microstructural Evolution at Elevated Temperature in Extruded AZ31 Magnesium Alloy

“…1,2) The lower forming temperature has been muchneeded in the engineering application field, as these forming temperatures are currently above 523 K. [2][3][4] It is necessary to accumulate the sufficient data about magnesium forming technologies at the temperatures below 523 K.…”

Suppression of Macroscopic Defects through the Control of Friction between Workpiece and Dies in a Forged Magnesium Alloy Part with Ribs

“…[2][3][4][5][6][7][8] The authors have already successfully fabricated plate-form parts with a boss in magnesium alloys by superplastic forging. 9,10) One of the principal types of defect in closed-die forging is extrusion-type defects, 11) which are formed when centrally located ribs and bosses, formed by extrusion-type flow, draw too much metal from the main body of the forging. Conical or valley-like surface defects may be formed for bosses or ribs, respectively, which results in poor quality of the surface appearance in the case of electrical and electronic appliances.…”